Surface subsidence simulation method and device under the condition of goaf overburden bed separation grouting

Abstract

The present invention relates to a method and device for simulating surface subsidence under the condition of goaf overburden separation grouting. The simulation method includes: S100, generalizing the strata in the study area; S200, constructing a three-dimensional engineering geological model of the study area; S300, determining the constitutive model, yield criterion, boundary conditions and calculation parameters in the three-dimensional engineering geological model; S400, setting a double-node state between the first grid group in the upper layer and the second grid group in the adjacent lower layer in the three-dimensional engineering geological model; S500, carrying out step-by-step mining, the separation in the target horizon starts to develop, and grids are filled into the separation space to simulate grouting; S600, the grouting slurry is transformed into grouting stone body, the grouting grid parameters are enhanced to stone body parameters, and at the same time the grouting pressure is withdrawn; until the mining of the working face is completed. The present invention realizes the whole-process simulation of separation grouting, which is close to the actual grouting process. It can predict the effect of reducing subsidence by engineering grouting and provide guidance for actual engineering.

Description

Technical Field

[0001] The present invention generally relates to the technical field of engineering geological simulation, and particularly relates to a method and device for simulating surface subsidence under the condition of overburden strata separation grouting in coal mining. Background Art

[0002] The exploitation of underground coal resources changes the stress balance state of the surrounding rock, which in turn leads to the redistribution and movement of the stress of the overlying strata. The movement and deformation of the overlying strata gradually transfer upward to the surface, resulting in surface settlement and deformation, which is called mining subsidence. The surface subsidence induced by the exploitation of these coal resources will inevitably damage the surface buildings and ecological environment.

[0003] In addition to actual projects, at present, the process of overburden strata separation grouting is mainly studied by numerical simulation. In order to evaluate the effect of reducing subsidence by overburden strata separation grouting, relevant scholars have proposed the concept of injection-extraction ratio, that is, the ratio of the mass of fly ash used for grouting to the total mass of the coal mined. In the current simulation of overburden strata separation grouting, discrete element software is mainly used, mostly in two-dimensional profiles. By presetting a series of different injection-extraction ratios, a fixed volume of slurry is filled into the preset separation space. By comparing the surface subsidence under different injection-extraction ratios, the control situation of surface subsidence under what injection-extraction ratio can meet the standard is inversely deduced.

[0004] The existing simulation methods have the following problems:

[0005] (1) The injection-extraction ratio is set in advance during grouting. Based on the control situation of surface subsidence after grouting, it is inversely deduced what injection-extraction ratio can meet the need for controlling surface subsidence. However, it is not clear whether the separation space can accommodate the required grouting volume.

[0006] (2) The separation space used during grouting is preset, but the actual separation space changes continuously with the coal mining. Therefore, the preset separation space cannot reflect the actual separation space situation, and the shape of the preset separation space is also different from that of the actual separation space.

[0007] (3) When simulating grouting by the existing methods, the medium filled into the separation space is basically set as a rigid body, and its volume does not change. But in reality, first, slurry is injected into the separation, and then the water in the slurry precipitates, and fly ash or gangue deposits in the separation space to control the movement and deformation of the overlying strata. The existing technical methods do not simulate the process of the grouting slurry turning into the grouting stone body.

[0008] (4) In actual projects, the slurry is injected into the separation space by using a grouting pump, and the current simulation methods cannot simulate the influence of the grouting pressure on the formation during the grouting process. Summary of the Invention

[0009] In view of the deficiencies of the prior art, the present invention proposes a new method for simulating surface subsidence under the condition of goaf overburden separated layer grouting, which can be realized based on FLAC 3D software, realizing the whole process simulation of separated layer grouting, which is close to the actual grouting process. It can predict the effect of reducing subsidence by engineering grouting and provide certain guidance for actual projects.

[0010] To achieve the above object, the technical solution of the present invention is as follows:

[0011] The present invention first provides a method for simulating surface subsidence under the condition of goaf overburden separated layer grouting, including: S100, collecting borehole data of the research area and generalizing the strata of the research area according to the collected borehole data; S200, constructing a three-dimensional engineering geological model of the research area, and the three-dimensional engineering geological model is divided into multiple grid groups; S300, determining the constitutive model, yield criterion, boundary conditions and calculation parameters of the three-dimensional engineering geological model; S400, setting the state of double nodes between the first grid group in the upper layer and the second grid group in the adjacent lower layer in the three-dimensional engineering geological model, so that discontinuous deformation can occur between the first grid group and the second grid group; S500, carrying out step-by-step mining, the separated layer in the target horizon begins to develop, and grids are filled into the separated layer space to simulate grouting; S600, the grouting slurry is transformed into grouting stone body, enhancing the grouting grid parameters to stone body parameters, and at the same time canceling the grouting pressure; S500 and S600 are cycled until the mining of the working face is completed.

[0012] Optionally, in S200, the construction of the three-dimensional engineering geological model of the research area includes:

[0013] Determining the mining working face;

[0014] Taking the working face as the center, expanding the three-dimensional engineering geological model around;

[0015] Performing grid division of the first size outside the working face range and performing grid division of the second size within the working face range, where the second size is smaller than the first size.

[0016] Optionally, in S300, the determination of the constitutive model, yield criterion, boundary conditions and calculation parameters includes:

[0017] Selecting the ideal elastic-plastic model as the constitutive model and using the Mohr-Coulomb criterion as the yield criterion;

[0018] Calculating that the boundary is a displacement constraint boundary condition, the normal displacement constraints are in the X-axis and Y-axis directions, and the bottom of the Z-axis direction is fully constrained;

[0019] The model boundary conditions are set as follows:

[0020] ① Single - factor horizontal constraint boundaries are set at the front, back, left, and right boundaries of the model;

[0021] ② The bottom boundary and the vertical direction of the model are set as fully - constrained bottom and vertical boundaries, and the initial accelerations are all set to zero;

[0022] ③ The top of the model is set as free, without restricting the constraint conditions;

[0023] The selection of physical and mechanical parameters is based on the laboratory test results of borehole cores in the research area collected and numerical simulation experience.

[0024] Optionally, in S400, setting the upper first grid group and the adjacent lower second grid group in a double - node state includes:

[0025] Determine the adjacent first grid group and second grid group, where the first grid group corresponds to the upper rock layer and the second grid group corresponds to the lower rock layer, associate the first grid group and the second grid group and share one or more nodes;

[0026] Set the elastic modulus of the first grid group to be greater than that of the second grid group;

[0027] Fill interface elements between the first grid group and the second grid group.

[0028] Optionally, in S500, filling the grid into the separated - layer space includes:

[0029] Continuously monitor the distance between double - nodes while carrying out step - by - step mining;

[0030] Judge whether the distance between double - nodes exceeds the preset value. When the distance between double - nodes exceeds the preset value, fill the grid into the separated - layer space.

[0031] Optionally, in S500, filling the grid into the separated - layer space includes:

[0032] Set the filled grid as a double - layer grid;

[0033] Assume that the filled grid is a fluid and set it with an isotropic elastic yield criterion;

[0034] Set the parameters of the upper - layer grid stronger and the parameters of the lower - layer grid weaker.

[0035] Optionally, in S500, filling the grid into the separated - layer space to simulate grouting further includes:

[0036] When the grouting grid is generated, set the grouting pressure of the grouting grid the same as that in the actual project.

[0037] Optionally, in S500, filling the grid into the separated - layer space to simulate grouting also includes:

[0038] Continue mining, the separated layer continues to develop, and the grid is stretched to simulate continuous grouting.

[0039] Optionally, setting the grouting pressure of the grouting grid the same as that in the actual project includes:

[0040] The grouting pressure consists of two parts. One part is the pump pressure of the grouting pump, and the other part is the head difference of the slurry from the ground surface to the grouting position.

[0041] Set the total grouting pressure of the two parts to be the same as that in the actual project.

[0042] The present invention also provides a surface subsidence simulation device under the condition of grouting in the separated layer of overlying strata caused by mining, including: one or more processors; and a storage device for storing a computer program, which, when executed by the one or more processors, enables the one or more processors to implement the foregoing simulation method.

[0043] The beneficial effect of the present invention compared with the prior art is: The present invention proposes a new type of surface subsidence simulation under the condition of grouting in the separated layer of overlying strata caused by mining, which can be realized based on FLAC 3D software, realizing the whole process simulation of separated layer grouting and being close to the actual grouting process. Specifically, at least one or more of the following beneficial effects can be achieved:

[0044] (1) When simulating the grouting in the separated layer of overlying strata, it is carried out synchronously during the coal seam mining process, and the separated layer space changes dynamically with the coal seam mining.

[0045] (2) The grouting simulation takes into account the influence of the actual grouting pressure on the grouting process.

[0046] (3) The grouting simulation takes into account the whole process from the initial injection of slurry to the change of slurry into grouting stone body.

[0047] (4) Instead of presetting the injection-extraction ratio, it simulates the real grouting process, analyzes the surface subsidence situation after grouting, rather than adjusting the injection-extraction ratio by analyzing the surface subsidence situation.

[0048] (5) This method can not only intuitively analyze the surface subsidence situation, obtain the exact result of the surface settlement value under the final grouting condition, but also analyze the control mechanism of grouting in the separated layer of overlying strata and the influence of grouting on the movement law of overlying strata through the dynamic grouting process.

[0049] (6) By comparing the surface subsidence under the non-grouting and grouting conditions, the surface subsidence control effect of the whole separated layer grouting project can be evaluated, providing certain guidance for actual projects. Description of the Drawings

[0050] To more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. Obviously, the drawings in the following description are only exemplary. For those of ordinary skill in the art, without creative efforts, other implementation drawings can be obtained by extending the provided drawings.

[0051] The structures, ratios, sizes, etc. shown in this specification are only used to cooperate with the content disclosed in the specification for those familiar with this technology to understand and read, and are not used to limit the limiting conditions under which the present invention can be implemented. Therefore, they do not have a substantial technical meaning. Any modification of the structure, change in the proportional relationship, or adjustment of the size, without affecting the effects that the present invention can produce and the purposes that can be achieved, should still fall within the scope covered by the technical content disclosed in the present invention.

[0052] Figure 1 is a flowchart of a surface subsidence simulation method under the condition of goaf overburden separation layer grouting according to some embodiments of the present invention;

[0053] Figure 2 is a schematic diagram of the double-node state in a three-dimensional engineering geological model according to some embodiments of the present invention;

[0054] Figure 3 is a schematic diagram of a grouting process according to some embodiments of the present invention;

[0055] Figure 4 is a schematic diagram of grid filling according to some embodiments of the present invention;

[0056] Figure 5 is a schematic diagram of forming a grouting stone body according to some embodiments of the present invention;

[0057] Figure 6 is a schematic diagram of a three-dimensional engineering geological model according to some embodiments of the present invention;

[0058] Figure 7 is a schematic diagram of a working face profile line according to some embodiments of the present invention;

[0059] Figure 8 is a curve graph of the change in the separation layer filling thickness during the mining process of a working face according to some embodiments of the present invention;

[0060] Figure 9 is a curve graph of the separation layer filling thickness in the direction perpendicular to the working face mining according to some embodiments of the present invention;

[0061] Figure 10 is a surface subsidence cloud map according to some embodiments of the present invention;

[0062] Figure 11It is a surface subsidence curve graph according to some embodiments of the present invention. Detailed implementation manners

[0063] To make the objectives, technical solutions and advantages of the embodiments of the present invention clearer and more understandable, the embodiments of the present invention will be further described in detail below in conjunction with the embodiments and the drawings. Herein, the illustrative embodiments of the present invention and their descriptions are used to explain the present invention, but not to limit the present invention.

[0064] It should be understood that the terms "include / comprise", "consist of" or any other variant thereof are intended to cover non-exclusive inclusion, so that a product, device, process or method including a series of elements not only includes those elements, but may also include other elements not explicitly listed when needed, or further includes elements inherent to such product, device, process or method. Without further limitation, the elements defined by the statements "include / comprise..." or "consist of..." do not exclude the existence of additional identical elements in the product, device, process or method including the said elements.

[0065] In the present invention, unless otherwise clearly specified and limited, the terms "upper", "lower", "front", "rear", "left", "right", "top", "bottom", "inner", "outer", etc. indicating the orientation or positional relationship are based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the indicated device, component or structure must have a specific orientation, be constructed or operated in a specific orientation, and should not be construed as a limitation to the present invention.

[0066] In addition, the terms "first" and "second" are only used for descriptive purposes, and cannot be understood as indicating or implying relative importance or implicitly indicating the quantity of the indicated technical features. Thus, the features defined with "first" and "second" may explicitly or implicitly include one or more of such features. In the description of the present invention, "a plurality of" means two or more, unless otherwise clearly and specifically defined.

[0067] The overburden separation grouting technology is a technique used to control surface subsidence during the underground coal resource mining process, which can effectively reduce surface subsidence and protect surface buildings and structures. The key stratum theory is the basic theory of this technology, which believes that in the overlying strata of the stope, the key strata play a partial or total control role in the movement and deformation of the strata. Simply put, the key strata are some hard rocks with relatively large thickness in the overlying strata of the mined coal seam. During the coal seam mining process, the bending deformation between the key strata and the strata below them is asynchronous, resulting in a separation space. Grouting into the separation space can support the upper key strata, thereby controlling the bending deformation of the upper strata and reducing surface subsidence. The grouting material for the overburden separation grouting technology is the slurry after mixing fly ash or coal gangue with water. These two materials are not soluble in water, but turn into stone bodies in the separation space after being injected, thereby controlling the settlement of the upper strata.

[0068] Based on the above theory, the implementation of the present invention will be described in detail below in combination with preferred embodiments and corresponding specific drawings.

[0069] Figure 1 The flowchart of the surface subsidence simulation method under the condition of mining-induced overburden separation grouting according to some embodiments of the present invention is shown. In some embodiments, refer to Figure 1 , including the following steps: S100, collect the borehole data of the research area, and generalize the strata of the research area according to the collected borehole data; S200, construct a three-dimensional engineering geological model of the research area, and the three-dimensional engineering geological model is divided into multiple grid groups; S300, determine the constitutive model, yield criterion, boundary conditions and calculation parameters in the three-dimensional engineering geological model; S400, set the state between the first grid group of the upper layer and the second grid group of the adjacent lower layer in the three-dimensional engineering geological model to a double-node state, so that discontinuous deformation can occur between the first grid group and the second grid group; S500, carry out step-by-step mining, the separation of the target horizon begins to develop, and fill the separation space with grids to simulate grouting; S600, the grouting slurry turns into a grouting stone body, enhance the grouting grid parameters to the stone body parameters, and at the same time cancel the grouting pressure; Loop S500 and S600 until the working face mining is completed.

[0070] In S100, collect the borehole data of the research area, and generalize the strata of the research area according to the collected borehole data.

[0071] In some embodiments, drilling data of the study area can be collected, and the rock formations in the study area can be generalized based on the drilling data. Specifically, the rock formations can be generalized according to different geological ages, and then they can be more finely stratified according to different lithologies within each geological age. Among them, lithology refers to some attributes that reflect the characteristics of rocks, such as color, composition, structure, cement, and cementation type, special minerals, etc. It should be understood that any method of stratification using lithology in the art can be used to implement the above steps, and the present invention is not limited to this. It should be noted that the study area can be the study area of ​​any soil layer or rock layer, and the present invention is not limited to this.

[0072] In S200, a three-dimensional engineering geological model of the study area is constructed, and the three-dimensional engineering geological model is divided into a plurality of grid groups.

[0073] The present invention adopts FLAC 3D The software constructs a three-dimensional engineering geological model of the study area.

[0074] According to theoretical analysis, the height of the detached layer decreases as it moves away from the working face. In some embodiments, in order to obtain a good simulation effect, constructing a three-dimensional engineering geological model of the study area includes: determining the mining working face; taking the working face as the center, expanding the three-dimensional engineering geological model to the surrounding areas; 3D In order to ensure the calculation speed, the first-size mesh is divided outside the working surface, and the second-size mesh is divided within the working surface, where the second size is smaller than the first size. That is, large-scale mesh division can be performed outside the working surface, and the mesh is divided more finely within the working surface.

[0075] In S300, a constitutive model, a yield criterion, boundary conditions and calculation parameters are determined in a three-dimensional engineering geological model.

[0076] In FLAC 3D A variety of constitutive models and yield criteria can be set in the software. According to the actual simulation calculation needs, appropriate constitutive models, yield criteria, boundary conditions and calculation parameters can be selected for calculation.

[0077] In some embodiments, the present invention selects an ideal elastic-plastic model as a constitutive model and uses the Mohr-Coulomb criterion as a yield criterion.

[0078] The calculation boundary is a displacement constraint boundary condition, the X-axis and Y-axis directions are normal displacement constraints, and the bottom of the Z-axis direction is a full constraint.

[0079] The model boundary conditions are set as follows:

[0080] ① Single factor level constraint boundaries are set on the front and back and left and right boundaries of the model;

[0081] ② The bottom boundary and the vertical direction of the model are set as fully constrained bottom and vertical boundaries, and the initial accelerations are all set to zero;

[0082] ③ The top of the model is set as free, without restricting the constraint conditions;

[0083] The selection of physical and mechanical parameters is based on the laboratory test results of borehole cores in the research area collected and numerical simulation experience. For example, the cores taken from on-site boreholes can be used for indoor tests to obtain the initial parameters required for model calculation, including parameters such as the elastic modulus, Poisson's ratio, cohesion, internal friction angle, unit weight, and tensile strength of rock masses in each rock layer. These parameters can also be obtained based on numerical simulation experience or combined with relevant engineering experience.

[0084] In S400, in the three-dimensional engineering geological model, the upper first grid group and the adjacent lower second grid group are set in a double-node state, so that discontinuous deformation can occur between the first grid group and the second grid group;

[0085] In some embodiments, Figure 2 is a schematic diagram of the double-node state in the three-dimensional engineering geological model according to some embodiments of the present invention. As described above, the key strata are the relatively thick hard rocks in the overlying strata of the mined coal seam, and usually include a main key stratum and one or more sub-key strata. The key strata are thicker in single layer thickness than other similar rock strata, and are harder than other rock strata, that is, they have a larger elastic modulus and higher strength. According to the key stratum theory, during the coal seam mining process, the key strata are the controlling rock strata. Generally speaking, when the key strata bend and deform, the bending and deformation of all or part of the overlying rock strata are synchronized and coordinated, while discontinuous deformation occurs between the key strata and the underlying rock strata, that is, the bending and deformation between the key strata and the underlying rock strata are not synchronized, thus generating a separation space under the relatively hard rock strata. Grouting into the separation can support the upper key strata, thereby controlling the bending and deformation of the upper rock strata and reducing the surface subsidence.

[0086] Since the model constructed by the FLAC 3D software is a continuous medium model, the common nodes are shared on the contact surfaces of the meshes divided by the model, and no space can be generated between the meshes, so the development of separation cannot be simulated. Therefore, in order to simulate the dynamic development process of separation, a double-node state is set between the relatively hard rock strata and the adjacent lower soft rock strata. Specifically, on the basis of the three-dimensional engineering geological model divided into multiple grid groups, at the layer positions where the development of separation may occur, the common nodes on the connecting surface of the two grid groups are split into two, and each uses a separate node.

[0087] In some embodiments, first determine the adjacent first grid group and second grid group, such as Figure 2As shown, where the first grid group corresponds to the upper rock layer and the second grid group corresponds to the lower rock layer. The first grid group and the second grid group are associated and share one or more nodes. Then, the elastic modulus of the first grid group is set to be greater than that of the second grid group to simulate the harder rock layer and its adjacent softer lower rock layer. Finally, after setting the double nodes, at the position of the double nodes, the upper and lower layer grids lose contact and the interaction relationship is lost. Therefore, interface elements need to be filled between the first grid group and the second grid group. After applying the interface elements, the connection between the two layer grids is re-established. In this way, by separating the nodes at the junction of the soft and hard rock layers and adding interface elements, discontinuous deformation can occur between the soft and hard rock layers, and thus the prerequisite for the generation of separation space between these layers is created, and this method will not interfere with the movement of the overlying rock.

[0088] In S500, step-by-step mining is carried out, and separation begins to develop in the target layer. Grids are filled into the separation space to simulate grouting.

[0089] In the present invention, referring to Figure 3 , Figure 3 is a schematic diagram of the grouting process according to some embodiments of the present invention. Step-by-step mining of the coal seam is carried out. The mining of the coal seam causes the movement of the overlying rock, and thus the development of separation. When the separation develops, grids are filled (corresponding to injecting slurry in actual engineering).

[0090] In some embodiments, during step-by-step mining, the distance between the double nodes is continuously monitored; it is judged whether the distance between the double nodes exceeds a preset value. When the distance between the double nodes exceeds the preset value, grids are filled into the separation space.

[0091] In some embodiments, it is set that whether the distance between the double nodes exceeds the preset value is 5 cm. Since grids need to be filled into the separation space, if the space is too small, it is easy to cause grid distortion error reporting and unable to calculate. When the distance between the double nodes exceeds 5 cm, the development of separation can be easily and accurately judged, and grid distortion error reporting will not occur in the simulation, ensuring the smooth progress of the calculation.

[0092] According to the actual engineering situation, several grouting holes will be pre-set on the ground during separation grouting, that is, grouting holes are pre-set before coal mining, which means drilling holes from the ground downwards, and grouting holes at different positions are selected for grouting according to the development of separation.

[0093] In the actual on-site engineering, grouting is carried out while mining. In this step, filling the grids is repeated during each step of mining to ensure that grouting simulation is carried out synchronously with the development of separation.

[0094] In some embodiments, referring to Figure 4 , Figure 4It is a schematic diagram of grid filling according to some embodiments of the present invention. Filling the separated layer space with a grid includes:

[0095] Set the filling grid as a double-layer grid;

[0096] Assume the filling grid is a fluid and set it to an isotropic elastic yield criterion;

[0097] Set the parameters of the upper layer grid stronger and the parameters of the lower layer grid weaker. Refer to Table 1 below for the grouting grid parameters.

[0098] Table 1: Grouting grid parameter table

[0099] Grouting grid Elastic modulus (Pa) Poisson's ratio <![CDATA[Density (g / cm 3 )]]> Upper layer <![CDATA[5×10 10 > 0.01 1000 Lower layer <![CDATA[1×10 4 > 0.01 1000

[0100] The reason for setting a double-layer grid with different parameters is as follows:

[0101] (1) The development of the separated layer under normal conditions is: generation - expansion - reduction - closure, and grouting starts when the separated layer just appears. During coal mining, the lower rock layer where the separated layer is located is constantly moving and deforming downward, and the separated layer space is constantly expanding. The parameters of the lower layer grid used for grouting are relatively low, which does not interfere with the continuous movement and deformation of the lower rock layer, and can continuously elongate along with the movement and deformation of the underlying rock mass. In this way, the simulation effect of continuous grouting can be achieved while the separated layer is developing dynamically.

[0102] (2) Since the constitutive relationship of the grouting grid set is an isotropic elastic constitutive relationship, the grid is not only easily stretched but also easily compressed. The separated layer space can be equivalently regarded as a simulation space. In such an environment, the fluid itself has the characteristic of being difficult to compress. If a single-layer grouting grid is set, it is difficult to achieve both the simulation of continuous grouting along with the movement of the overlying rock layer and the simulation effect of the fluid being difficult to compress to support the overlying rock layer. Therefore, the present invention sets up a double-layer grid, sets the parameters of the upper layer grid stronger and the parameters of the lower layer grid weaker, so as to equivalently simulate the effect that the upper layer liquid is difficult to compress and the lower layer liquid can simulate continuous grouting along with the movement of the overlying rock layer.

[0103] In some embodiments, continue to refer to Figure 3 , filling the separated layer space with a grid further includes: when the grouting grid is generated, set the grouting pressure on the grouting grid the same as that in the actual project.

[0104] In the present invention, when the grouting grid is generated, set the grouting pressure on the grouting grid the same as that in the actual project, and by considering the influence of the actual grouting pressure on the grouting process, to simulate the real filling effect.

[0105] In some embodiments, the grouting pressure consists of two parts. One part is the pump pressure of the grouting pump, and the other part is the head difference of the grout from the ground surface to the grouting position. Considering both the pump pressure and the head difference of the grouting path, setting the sum of the two parts of the grouting pressure to be the same as the actual engineering grouting pressure can simulate the real engineering grouting effect.

[0106] In some embodiments, continue to refer to Figure 3 , filling the separated seam space with a grid further includes: continuous mining, continuous development of the separated seam, elongation of the grid, and simulating continuous grouting through the elongation of the grid. Thus, it can be seen that when the present invention simulates overburden separated seam grouting, it is carried out synchronously during the coal seam mining process. The separated seam space changes dynamically with the coal seam mining, realizing the whole-process simulation of separated seam grouting and approaching the actual grouting process.

[0107] In S600, the grouting slurry is transformed into a grouting stone body, the grouting grid parameters are enhanced to stone body parameters, and at the same time, the grouting pressure is cancelled.

[0108] It should be understood that the grouting grid here is the grid filled in S500 above for simulating grouting, and is called the grouting grid.

[0109] Based on the actual situation, ten grouting holes are preset before coal seam mining, with each grouting hole spaced 50 m apart, and grouting is carried out sequentially starting from the first grouting hole.

[0110] When the coal seam is mined to a certain number of meters, a separated seam starts to develop at a certain position, and the grouting grid is filled. Subsequently, the coal seam is mined 200 m further backward. At this time, grouting is no longer carried out near this position, and it is considered that the grouting slurry at this position has been transformed into a grouting stone body. The grouting grid parameters are enhanced to the parameters of the stone body, and at the same time, the grouting pressure is cancelled. As Figure 5 shown, Figure 5 is a grouting simulation schematic diagram according to some embodiments of the present invention. After grouting the separated seam space, the slurry solidifies into a grouting stone body. The separated seam space is affected by the stone body. The stone body supports the key stratum upward and prevents the soft rock from deforming downward, thereby effectively preventing the further development of the separated seam.

[0111] Loop through S500 and S600 until the working face mining is completed.

[0112] The grouting simulation of the present invention considers the whole process from the initial injection of the slurry to the transformation of the slurry into a grouting stone body, and takes into account the influence of the actual grouting pressure on the grouting process during this process. It is closer to the actual situation, the simulation effect is more real, and the simulation result is more accurate (which can be reflected in the engineering examples hereinafter).

[0113] Engineering example:

[0114] Taking a certain working face in a coal mine in City B, Province A of this invention as an example, the surface subsidence under the goaf overburden grouting is simulated and analyzed.

[0115] Step (1): Collect the borehole data of the research area, and generalize the strata of the research area according to the collected borehole data.

[0116] The coal seam mined in the research area is located in Province A. The strata from above the coal seam to the surface are simulated and calculated. A total of 34 borehole lithology data near the research area are collected this time. Now, the strata of the research area are generalized based on the borehole data.

[0117] First, generalize the strata based on different geological eras.

[0118] Secondly, within each geological era, further divide it more carefully according to different lithologies. This time, the strata of the research area are divided into 17 layers.

[0119] Step (2): Establish a three-dimensional refined engineering geological model.

[0120] See Figure 6 , Figure 6 is a schematic diagram of a three-dimensional engineering geological model according to some embodiments of the present invention. The working face mining direction is 1140 m long. Taking this direction as the x-axis direction of the three-dimensional geological model, and the mining direction is the positive x-axis direction. Taking the direction perpendicular to the working face mining direction as the y-axis direction of this three-dimensional geological model, and the positive z-axis direction points from low altitude to high altitude. The model extends 1000 m outward along the mining boundary of the working face on the positive and negative semi-axes of the x-axis and y-axis respectively, as the model boundary of this three-dimensional engineering geological model. The model is 3180 m long in the x-axis direction, 2280 m long in the y-axis direction, and about 850 m high in the z-axis direction.

[0121] Step (3): Determine the constitutive model, yield criterion, boundary conditions and calculation parameters.

[0122] The calculation boundary is a displacement constraint boundary condition. The x-axis direction and y-axis direction are normal displacement constraints, and the bottom of the z-axis direction is fully constrained. The model boundary conditions are set as follows:

[0123] ① Single-factor horizontal constraint boundaries are set on the front, back, left and right boundaries of the model;

[0124] ② The bottom boundary of the model and the vertical direction are set as fully constrained bottom and vertical boundaries, and the initial accelerations are all set to zero;

[0125] ③ The top of the model is set as free, without restricting the constraint conditions;

[0126] This time, the ideal elastoplastic model is selected as the constitutive model, and the Mohr-Coulomb criterion is used as the yield criterion.

[0127] The selection of physical and mechanical parameters is based on the laboratory test results of borehole cores in the research area collected and numerical simulation experience.

[0128] Step (4): Set the double-node state.

[0129] Before the step-by-step excavation simulation calculation of the model, separate the nodes between the upper hard rock and the lower soft rock layers and set them to the double-node state. Subsequently, set the interface element at the layer where the double nodes are set.

[0130] Step (5): Model calculation.

[0131] By carrying out step-by-step mining of the working face, to be closer to the actual situation, the mining step distance of the working face is set to 10 m per step, and a total of 114 steps are mined.

[0132] Step (6): Simulate the grouting process synchronously during the mining process of the working face.

[0133] The following analyzes the grouting effect:

[0134] See Figure 7 , Figure 7 is a schematic diagram of the cross-section line of the working face according to some embodiments of the present invention. The specific information of the cross-section line is as follows:

[0135] (1) a-a cross-section: Along the mining direction of the working face, located on the central axis of the mining direction of the working face, that is, consistent with the coal seam mining direction;

[0136] (2) b-b cross-section: Perpendicular to the mining direction of the working face, 200 m away from the open-off cut position;

[0137] (3) c-c cross-section: Perpendicular to the mining direction of the working face, 400 m away from the open-off cut position;

[0138] (4) d-d cross-section: Perpendicular to the mining direction of the working face, 800 m away from the open-off cut position;

[0139] (5) e-e cross-section: Perpendicular to the mining direction of the working face, 1000 m away from the open-off cut position;

[0140] It is easy to understand that the open-off cut refers to the excavation along the starting line of the coal mining face, which can be understood as the place where the coal mining of the working face begins.

[0141] 1. Analysis of the separated layer filling thickness in the direction parallel to the mining direction of the working face.

[0142] In the direction parallel to the mining direction of the working face (a-a cross-section), see the separated layer filling thickness on the central axis profile line of the working face Figure 8 , Figure 8It is a schematic diagram of the variation curve of the separated seam filling thickness during the working face mining process according to some embodiments of the present invention. Through separated seam grouting, the separated seam space is effectively supported, the breaking of the sub-key strata is prevented, and thus the surface subsidence is hindered. Finally, when the grouting is completed, as shown in (f) of Figure 8 Since the separated seam itself develops less near the open-off cut and the stop line, the grouting volume is less. While in the section of the working face from 200 m to 1000 m, the grouting volume is relatively uniform, and the maximum filling thickness of the separated seam on this profile line is about 3.3 m.

[0143] 2. Analysis of the separated seam filling thickness in the direction perpendicular to the working face mining direction.

[0144] In the direction perpendicular to the working face mining direction (sections b-b, c-c, d-d, e-e), referring to Figure 9 , Figure 9 It is a curve graph of the separated seam filling thickness in the direction perpendicular to the working face mining direction according to some embodiments of the present invention. It can be seen from the figure that the separated seam space develops with the characteristics of large thickness in the middle and small thickness on both sides in the direction perpendicular to the working face mining direction, showing an arched feature. The separated seam filling thickness is the largest at the middle position of the curve, that is, the separated seam filling thickness is the largest on the central axis of the working face in the working face mining direction. However, it can also be observed that the maximum separated seam filling thickness at different positions is different. Figure 9 In

[0145] 3. Analysis of the surface subsidence effect.

[0146] Referring to Figure 10 , Figure 11 , Figure 10 It is a surface subsidence nephogram according to some embodiments of the present invention. Figure 11It is a surface subsidence curve graph according to some embodiments of the present invention. Through analysis, it can be found that under the condition of grouting into the separated strata, during the mining process of the working face, there is still a continuous subsidence process on the surface, and it is relatively similar to the surface subsidence law under the condition of non-grouting, but the settlement amount is smaller, indicating that grouting effectively controls the key strata, reduces the movement and deformation of the strata above the key strata, and thus controls the surface subsidence. The surface settlement rate is slow, and the subsidence center continuously approaches the middle position of the working face as the working face is mined. When the mining of the working face is completed, the working face reaches full mining, and the maximum surface settlement is about 0.78 m. With a coal seam thickness of 5.5 meters, the surface subsidence coefficient is 0.142. Thus, the simulation method of the present invention can obtain the exact result of the surface settlement value under the final grouting condition, not only can intuitively analyze the surface subsidence situation, but also can analyze the separated strata grouting control mechanism and the influence of grouting on the movement law of overlying strata through the dynamic grouting process.

[0147] According to some embodiments, the present invention also provides a surface subsidence simulation device under the condition of separated strata grouting in overlying strata caused by mining, including: one or more processors; and a storage device for storing computer programs. The processor can be any suitable processor in the art, such as a CPU, etc. The storage device can be used to store computer programs, such as FLAC 3D software. When the computer program is executed by one or more processors, one or more processors are caused to implement the simulation method described above.

[0148] The present invention proposes a new surface subsidence simulation under the condition of separated strata grouting in overlying strata caused by mining, which can be implemented based on FLAC 3D software, realizes the whole process simulation of separated strata grouting, and is close to the actual grouting process. While the separated strata are continuously developing, grouting simulation is synchronously carried out into the separated strata, taking into account the actual grouting pressure and the whole process of the grout turning into grouting stone body. The injection-production ratio is not preset in advance, but the real grouting process is simulated, and the surface subsidence situation after grouting is analyzed, rather than adjusting the injection-production ratio by analyzing the surface subsidence situation. It can intuitively analyze the mechanism of reducing subsidence by grouting of the separated strata grouting technology, and can intuitively analyze the whole process of the separated strata, predict the engineering grouting subsidence reduction effect, and provide certain guidance for actual projects.

[0149] Although several specific implementation details are included in the above discussion, these should not be construed as limiting the scope of the present invention. Certain features described in the context of separate embodiments can also be implemented in combination in a single implementation. Conversely, the various features described in the context of a single implementation can also be implemented separately or in any suitable sub-combination in multiple implementations.

[0150] In addition, although the operations are depicted in a particular order, this should be understood as requiring that the operations be performed in the particular order shown or in sequential order, or that all of the illustrated operations be performed to achieve the desired result. In certain circumstances, multitasking and parallel processing may be advantageous. Similarly, although several specific implementation details are included in the above discussion, these should not be construed as limiting the scope of the present invention. Certain features that are described in the context of separate embodiments may also be implemented in combination in a single implementation. Conversely, the various features that are described in the context of a single implementation may also be implemented separately or in any suitable subcombination in multiple implementations.

[0151] The embodiments of the present invention have been described above. The above description is exemplary and not exhaustive, and is also not limited to the disclosed embodiments. Many modifications and variations will be apparent to those of ordinary skill in the art without departing from the scope and spirit of the described embodiments. The choice of terms used herein is intended to best explain the principles of the embodiments, the practical application, or improvements made to the technology in the market, or to enable other ordinary skill in the art to understand the embodiments disclosed herein.

Claims

1. A method for simulating surface subsidence under the condition of goaf overlying strata separation grouting, characterized in that, it includes: S100, collecting borehole data of the research area, and generalizing the strata of the research area according to the collected borehole data; S200, constructing a three-dimensional engineering geological model of the research area, and dividing the three-dimensional engineering geological model into multiple grid groups; S300, determining the constitutive model, yield criterion, boundary conditions and calculation parameters of the three-dimensional engineering geological model; S400, setting the state of double nodes between the first grid group in the upper layer and the second grid group in the adjacent lower layer in the three-dimensional engineering geological model, so that discontinuous deformation can occur between the first grid group and the second grid group; wherein, setting the state of double nodes between the first grid group in the upper layer and the second grid group in the adjacent lower layer includes: determining the adjacent first grid group and second grid group, wherein the first grid group corresponds to the upper rock, the second grid group corresponds to the lower rock, associating the first grid group and the second grid group and sharing one or more nodes; setting the elastic modulus of the first grid group to be greater than the elastic modulus of the second grid group; filling interface elements between the first grid group and the second grid group; S500, carrying out step-by-step mining, the separation of the target horizon starts to develop, and filling grids into the separation space to simulate grouting; wherein, filling grids into the separation space further includes: when the grouting grid is generated, setting the grouting pressure same as the actual project for the grouting grid; and, setting the grouting pressure same as the actual project for the grouting grid includes: the grouting pressure consists of two parts, one part is the pump pressure of the grouting pump, and the other part is the head difference of the grout from the ground surface to the grouting position; S600, the grouting slurry is transformed into grouting stone body, enhancing the parameters of the grouting grid to the parameters of the stone body, and at the same time canceling the grouting pressure; repeating S500 and S600 until the mining of the working face is completed.

2. The simulation method according to claim 1, characterized in that, in S200, constructing the three-dimensional engineering geological model of the research area includes: determining the mining working face; centering on the working face, expanding the three-dimensional engineering geological model around; carrying out grid division of the first size outside the range of the working face, and carrying out grid division of the second size within the range of the working face, wherein the second size is smaller than the first size.

3. The simulation method according to claim 1, characterized in that, in S300, determining the constitutive model, yield criterion, boundary conditions and calculation parameters includes: selecting an ideal elastoplastic model as the constitutive model and using the Mohr-Coulomb criterion as the yield criterion; the calculation boundary is a displacement constraint boundary condition, the normal displacement is constrained in the X-axis and Y-axis directions, and the bottom in the Z-axis direction is fully constrained; the model boundary conditions are set as follows: ① Single-factor horizontal constraint boundaries are set for the front, back, left and right boundaries of the model; ② The bottom boundary of the model and the vertical direction are set as fully constrained bottom and vertical boundaries, and the initial accelerations are all set to zero; ③ The top of the model is set as free without restricting the constraint conditions; The selection of physical and mechanical parameters is based on the laboratory test results of borehole cores in the research area collected and numerical simulation experience.

4. The simulation method according to claim 1, wherein, in S500, the filling grid into the separated layer space includes: continuously monitoring the distance between the two nodes while carrying out step-by-step mining; judging whether the distance between the two nodes exceeds a preset value, and when the distance between the two nodes exceeds the preset value, filling the grid into the separated layer space.

5. The simulation method according to claim 1, wherein, in S500, the filling grid into the separated layer space includes: setting the filling grid as a double-layer grid; assuming that the filling grid is a fluid and setting an isotropic elastic yield criterion; setting the parameters of the upper layer grid stronger and the parameters of the lower layer grid weaker.

6. The simulation method according to claim 1, wherein, in S500, the filling grid into the separated layer space to simulate grouting further includes: continuing to mine, the separated layer continues to develop, and stretching the grid to simulate continuous grouting.

7. The simulation method according to claim 1, wherein, the setting of the grouting pressure of the grouting grid the same as that in the actual project further includes: setting the sum of the grouting pressures of the two parts to be the same as the grouting pressure in the actual project.

8. A surface subsidence simulation device under the condition of goaf overburden separated layer grouting, comprising: one or more processors; and a storage device for storing a computer program, which when executed by the one or more processors enables the one or more processors to implement the simulation method according to any one of claims 1 to 7.

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